Nightmare Fuel: Getting there by the first chapter after the prologue. "Zirah would kill a baby just to stop him crying"... made even worse because he still suffers from Cuteness Proximity. It's just creepy.
"Creepy" sells Zirah a million miles short of the pants-wetting, throat-constricting, limb-trembling horror that he is capable of.
Tear Jerker: Seriously, this story WILL reduce you to a sobbing wreck.
The Woobie: Caphriel.Ok, he's generally pretty stoic about it, but read that last chapter and tell me you don't want to give him a hug, thank him for everything he's done, and let Canon!Aziraphale fuss over him for a while.